The 50-year-old has only made one new addition to his squad since his arrival from Everton in young Uruguayan defender Guillermo Varela from Penarol.
Moyes has since been frustrated in his attempts to land Fabregas, however is hopeful new faces will soon be arriving at Old Trafford.
"I couldn't tell you if there will be another bid," Moyes said.
"Obviously we will take stock of it and consider what we are going to do next.
"But what we have here is a really good squad of players already.
"You mustn't forget about the quality that is already here at Manchester United. Undoubtedly we are hoping to add to it.
"I am quite confident we will do, certainly before the window shuts."
Last week Barcelona coach Gerardo Martino sent a defiant message to United claiming that Fabregas was not for sale and they were "counting on" the former Arsenal midfielder.
United had a first bid of £25m and a second of £30m rejected by the La Liga champions earlier this month.
And the former Everton boss refuted suggestions that the on-going saga would be an embarrassment to United if the Spanish international did not sign.
"I never at any time said I knew we would get him," he said.
"I just said we had made offers.
"They have been rejected. We will take stock from there and decide where we go from there."
One player who is also on the United manager's radar is Real Madrid playmaker Luka Modric.
The former Tottenham midfielder has struggled to hold down a regular first-team place in the Spanish capital and his future is uncertain under new manager Carlo Ancelotti.
Last season the £30m Croatian international was able to show off his undoubted ability at Old Trafford, scoring as Madrid dumped United out of the Champions League.
